Single-lens reflex camera with an automatic aperture control device

ABSTRACT

A single-lens reflex camera with an automatic aperture control device comprises a photoelectric element for converting the intensity of light from an object through an objective lens into an electrical signal and disposed so that the light passed thereto through the lens may be intercepted during film exposure. Synchro contacts for flash photography are provided and adapted to close upon shutter release, and aperture control means is provided for varying the aperture opening of the objective lens. A motor for operating the aperture control means is connected with a circuit including the photoelectric element to control the aperture control means in accordance with the electrical signal. Means for stopping the motor is connected with the circuit to cut off a current to the motor upon closing of the synchro contacts, thereby stopping the motor.

United States Patent [1 1 Shimomura [111 3,772,974 1 Nov. 20, 1973SINGLE-LENS REFLEX CAMERA WITH AN AUTOMATIC APERTURE CONTROL DEVICE JunShimomura, Tokyo, Japan [30] Foreign Application Priority Data Sept. 2,1971 Japan 46/78861 [52] US. Cl. 95/10 CD, 95/42, 95/64 D [51] Int. ClG03b 7/08, G03b 9/02, G03b 9/70 [58] Field of Search 95/10 C, 10 CD, 10CE,

[5 6] References Cited UNITED STATES PATENTS Yaskhiro Namba et a1 95/42Takamoshi Sato et a]. 95/64 D Westhaver 95/10 CD X Minneste, Jr.....95/10 CD X 3,592,116 7/1971 Ritze 95/10 CD X Primary Examiner-Joseph F.Peters, Jr.

Attorney-Joseph M. Fitzpatrick et a1.

[5 7] ABSTRACT A single-lens reflex camera with an automatic aperturecontrol device comprises a photoelectric element for converting theintensity of light from an object through an objective lens into anelectrical signal and disposed so that the light passed thereto throughthe lens may be intercepted during film exposure. Synchro contacts forflash photography are provided and adapted to close upon shutterrelease, and aperture control means is provided for varying the apertureopening of the objective lens. A motor for operating the aperturecontrol means is connected with a circuit including the photoelectricelement to control the aperture control means in accordance with theelectrical signal. Means for stopping the motor is connected with thecircuit to cut off a current to the motor upon closing of the synchrocontacts, thereby stopping the motor.

3 Claims, 1 Drawing Figure SINGLE-LENS REFLEX CAMERA WITH AN AUTOMATICAPERTURE CONTROL DEVICE I BACKGROUND OF THE INVENTION 1. Field of theInvention This invention relates to cameras with automatic aperturecontrol devices, and more particularly to such devices of the type inwhich an electrical signal of a magnitude relative to the brightness ofan object to be photographed is compared with an electrical signal, themagnitude of which is determined by the setting of exposure adjustingfactors such as shutter speed, film sensitivity, etc., to control theaperture opening and balance the two electrical signals. That is, thepresent invention is concerned with such control devices in whichaperture control means is driven in a direction to close the lensaperture when the object is relatively bright; and in a direction toopen the lens aperture when the object is relatively dark.

2. Description of the Prior Art If an automatic aperture control deviceof the described type is applied to a TTL type single-lens reflexcamera, in which light passed through a picture-taking lens is meteredto determine the exposure, a problem would be encountered in that lightwill not reach the light receiving portion of the camera when theshutter is released. This would be caused by the shifting of a mirrorwhere the light receiving portion is disposed, for example, in theview-finder system of the single-lens reflex camera. Also, even if thelight receiving portion comprises a photoelectric element or an opticalmember for passing light to a photoelectric element disposed behind themirror at least a portion of which passes light therethrough, thephotoelectric element or the optical member must be retracted out of theprincipal optical path during photography so as not to prevent film frombeing exposed to light, and this again hinders the light passed throughthe picture-taking lens from reaching the light receiving portion.

The result would be that, upon shutter release, a signal equivalent to arelatively dark object would be supplied to the automatic aperturecontrol device to drive the lens aperture in the opening direction, thusproviding an over-exposure.

Such a phenomenon has a serious adverse effect inasmuch as a greaterlength of film exposure time permits the aperture to be increasinglyopened during such exposure time.

As a solution to such problem, the prior art has proposed a memorydevice for storing the intensity of light from an object, just prior toshutter release, to be operated when the shutter button is depressed andbefore the reflecting mirror shifts; and also various types of circuitrytherefor. Such a memory device, however, is not only considerablycomplicated in its electronic circuitry, but also suffers much fromspace limitations for incorporating it into a camera, even if it isformed into a compact integrated circuit.

SUMMARY OF THE INVENTION The present invention proposes a solution tothe above-noted problem without resorting to any memory device of thedescribed type.

According to the present invention, a single-lens reflex camera,provided with an automatic aperture control device, comprises means forconverting into an electrical signal the intensity of light passed froman object through an objective lens. These means include a photoelectricelement disposed so that the light passed thereto through the objectivelens may be intercepted during the exposure of the film to light. Thecamera further comprises synchro contacts for use during flashphotography and adapted to close upon shutter release, and aperturecontrol means for varying the size of the aperture opening of theobjective lens. A motor, for operating the aperture control means, isconnected with a circuit including the photoelectric element to controlthe aperture control means in accordance with the electrical signal fromthe circuit so as to provide a proper exposure. Means for stopping themotor are connected with the circuit to cut off the current to the motorupon closing of the synchro contacts, thereby to stop the motor.

The synchro contacts are closed at the latest when the shutter of thecamera has been fully opened.

The electrical signal may occur in one of three magnitudes. Thus, afirst signal may be produced for overexposure, a second for properexposure, and a third for under-exposure. The first electrical signal isused to revolve the motor in one direction, the second is used to stopthe motor, and the third is used to revolve the motor in the reversedirection.

There has thus been outlined rather broadly the more important featuresof the invention in order that the detailed description thereof thatfollows may be better understood, and in order that the presentcontribution to the art may be better appreciated. There are, of course,additional features of the invention that will be described hereinafterand which will form the subject of the claims appended hereto. Thoseskilled in the art will appreciate that the conception upon which thisdisclosure is based may readily be utilized as a basis for the designingof other structures for carrying out the several purposes of theinvention. It is important, therefore, that the claims be regarded asincluding such equivalent construction as do not depart from the spiritand scope of the invention.

BRIEF DESCRIPTION OF THE DRAWING A specific embodiment of the inventionhas been chosen for purposes of illustration and description, and isshown in the accompanying drawing, forming a part of the specificationwherein:

The single FIGURE illustrates the principle underlying an embodiment ofthe present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing, apentaprism l, a condenser lens 7 disposed below the pentaprism andwithin the camera body, a focusing screen 8, a mirror 10a and a lens 2together constitute a known viewfinder system for single-lens reflexcamera. A condenser lens 6 is disposed behind the pentaprism l andopposed to the rear or exit surface la thereof so as to collect thelight passed through the focusing screen 8 onto a photoelectric elementRc. A mirror drive lever 12 is pivotally mounted to the camera body bymeans of a shaft 11 and has a pin 12a studded at one end thereof, whichpin is in engagement with a mirror support plate 10. The mirror 10a isintegral with the support plate 10 and is supported, for pivotalmovement, about a shaft 9. One end 12b of the mirror drive lever 12 isshown to be in engagement with an insulator plate 13 attached to one endof a contact 14 so that the contact 14 and a contact 16, engageable withthe contact 14, are slightly spaced apart with a clearance 16amaintained therebetween. The contact 14 is held by and between insulatorplates 17 and 18 fixed to the camera body and is normally biasedleftwardly, as viewed, by its own resiliency so as to be moved intoengagement with the contact 16 upon clockwise rotation of the mirrordrive lever 12 because the end 12b thereof is then disengaged from theinsulator plate 13. A drum 21 is rotatable about a shaft 22 in thedirection of arrow A3 with the movement of the forward shutter blade(not shown) which opens the shutter. A cam 23 is secured to the shaft 22and is formed with a projection 23a which, in the fully open position ofthe forward shutter blade, is engageable with an insulator plate 14battached to a contact 14a integral with the aforesaid contact 14,thereby to move the contact 1411 rightwardly, as viewed, into engagementwith a contact 19 supported by the insulator plate 18. The contact 14ais normally biased leftwardly by its own resiliency and the end thereofis stopped by a pin 25 of insulative material secured to thecorresponding end of a synchro change-over lever 26, with a clearance19a maintained between the contact 14a and the contact 19. The insulatorplate 18 spaces the contacts 14, 14a apart from the contact 19. Thesynchro change-over lever 26 is pivotally mounted to the camera by meansof a pin 27 and has a projection 26a normally biased into engagementwith a change-over cam 28 by a spring 24.

The change-over cam 28 is connected to a shutter speed dial 5 by a shaft5a and includes a largerdiametered portion 28b and a smaller-diameteredportion 28a. The cam 28 is such that the portion 28b is engaged with theprojection 26a of the change-over lever 26 when the shutter speed is setto a high speed such as 1/1000 sec. to H125 sec. and that the portion28a is engaged with the projection 26a when the shutter speed is set to1/60 sec. to 1 sec. The aforesaid contact 16 is connected with a synchroterminal 30a by a conductor 29, and the contact 19 is connected with asynchro terminal 30b by a conductor 20.

Description will now be made of the construction of the automaticaperture control device of the present invention.

in the illustrated embodiment, the photoelectric element Rc, such as aCdS cell, is connected in series with a variable resistor Rv. One end ofthe element Re is connected with the positive terminal of an electricpower source E1, and one end of the resistor Rv is connected with thenegative terminal of an electric power source E2. The point ofconnection between the element Re and the resistor Rv is connected withthe bases of PNP transistor T1 and NPN transistor T2 which serve asbridge balance detecting transistors. A bias diode D is inserted betweenresistors R1 and R2, which cooperate with element Re and resistor Rv toconstitute a bridge circuit to apply a bias between the emitters of thedetecting transistors T1 and T2 so as to reduce the insensitive zone ofthese transistors.

One end of the resistor R1 is connected with the positive terminal ofthe electric power source El and one end of the resistor R2 is connectedwith the negative terminal of the electric power source E2. Thecollectors of the transistors T1 and T2 are connected with the bases ofNPN transistor T4 and PNP transistor T3, respectively. The emitter ofthe PNP transistor T3 is connected with the positive terminal of theelectric power source E1 and the collector thereof is connected with thecollector of the NPN transistor T4 through protective resistors R3 andR4. The emitter of the transistor T4 is connected with the negativeterminal of the electric power source E2. An aperture control motor M isa reversible motor whose direction of rotation is determined by the ONand OFF" states of NPN and PNP switching transistors T5 and T6, thebases of which are connected with the point of connection between theresistors R3 and R4 and the emitters of which are connected with oneterminal of the motor M. The collector of the transistor T5 is connectedwith the positive terminal of the electric power source E1 and thecollector of the transistor T6 is connected with the negative terminalof the electric power source E2. The other terminal of the motor M isconnected with an intermediate tap m, which is connected with thenegative and positive and terminals of the electric power sources E1 andE2, respectively.

The mechanical output of the aperture control motor M, such as therotation of its shaft, is integrally associated via known mechanicalinterlocking means 33, 34, 35 with a preset aperture ring 3 for thepicturetaking lens, and with a slide brush 36 forming, with the variableresistor Rv, an exposure factor adjusting means. I

The shutter speed dial 5 is also associated via known mechanicalinterlocking means 32 with the exposure factor adjusting variableresistor Rv to displace this resistor itself. It will be apparent thatthe mechanical interlocking means 32 may be constructed so that filmsensitivity may also contribute to the displacement of the resistor Rv.

The mechanical interlocking means 35 need not necessarily be associatedwith the preset aperture ring 3 for lens 2, but alternatively, it may beformed as the stop member for an automatic diaphragm actuating member inthe normally open lens for a single-lens reflex camera. Such stop memberfor the automatic diaphragm actuating member need not necessarily belocated within the lens, but may be associated with the camera body.

Where the lens 2 is provided with a conventional diaphragm instead ofthe normally open preset (automatic) diaphragm for use with asingle-lens reflex camera, the mechanical interlocking means 34 may beeliminated and the photoelectric element Rc will be in the form of aso-called light-quantity feedback system whereby the aperture isautomatically adjusted so as to balance the bridge. The presentinvention is essentially applicable to such system as well.

In the automatic aperture control circuit, terminals 31a and 31b, forinsertion into the aforesaid synchro terminals 30a and 30b, are led outfrom the base and emitter of the transistor T4.

Further, a normally open switch S1 is provided which can short-circuitthe base-emitter of the transistor T4, and a normally open switch S2 isprovided which can short-circuit the base-emitter of the transistor T3.The switches S1 and S2 form the so-called limit switches and are of suchmechanical construction that the switch S1 is closed when the lensassumes its open aperture and that the switch S2 is closed when the lensassumes its minimum aperture.

The operation of the present invention will be described in sequencehereunder.

In case of under-exposure (i.e., when the quantity of light incident onthe photoelectric element Re, which is designated by the resistancevalue of the variable resistor Rv determined by a combination ofexposure adjusting factors, is greater than the actual quantity ofincident light from the object to be photographed), the resistance valueof the element RC is higher than that during the balance of the bridge,thus reducing the base potentials of the transistors T2 and T1. Whenthese base potentials drop by a predetermined value below a referencepotential determined by the bias voltage applied to the emitter of thetransistor T1, i.e., drop below the base-emitter voltage necessary forthe transistor T1 to conduct, the transistor T1 becomes conductive. Thecollector current of the transistor T1, in turn, renders the transistorT4 conductive. This reduces the base potentials of the transistors T6and T5, thus rendering the transistor T6 conductive. As a result, acurrent in the direction of arrow A2 flows through the circuit E2 M T6to start to revolve the aperture control motor M in a direction to openthe lens aperture.

This is accomplished by the interlocking means 33, 35 mechanicallyconnecting the motor M to the preset aperture ring 3. As statedpreviously, the interlocking means 34 is designed so as to vary theexposure factor adjusting variable resistor Rv in a direction toincrease its resistance value Rv, and thus the potential at the point ofconnection between the photoelectric element Rc and the variableresistor Rv rises to a certain level, whereupon the base potential ofthe transistor T1 also rises and this transistor turns off, andaccordingly the transistors T4 and T6 also turn off to deenergize theaperture control motor M, thus completing the adjustment of the apertureto a proper value.

if the object becomes brighter, the resistance value of thephotoelectric element Rc is reduced to increase the potential at thepoint of connection between Re and Rv, i.e., the base voltages of thetransistors T] and T2, thus breaking the balance of the bridge. Thus,the transistor T2 conducts to turn on the transistors T3 and T5 topermit a current to flow through the circuit E1 M T5 in the direction ofarrow A1, thus revolving the aperture control motor M in the directionopposite to that previously described. In response thereto, the presetaperture ring.3 for the lens is rotated in a direction to close the lensaperture and, at the same time, the mechanical interlocking means 34reduces the resistance of the variable resistor Rv to adjust theresistor Rv in a direction to balance the bridge again. With suchadjustment, the potential at the point of connection between Re and Rvis reduced to turn off the transistor T2 and accordingly the transistorsT3 and T5, thus deenergizing the aperture control motor M to restore thebalanced state of the bridge and to provide a proper exposure. Thetransistors T3 T6 and resistors R3 and R4 function as control means forthe motor M.

The operation of the cameras synchro mechanism will be describedhereunder. Depression of the shutter button causes the mirror a and itssupport plate 10 to rotate clockwise about the shaft 9 to intercept thepassage of the light passed through the picture-taking lens 2 andreflected by the mirror 10a to travel through the pentaprism l andcondenser lens 6 to the photoelectric element Rc. As the mirror supportplate 10 is rotated clockwise by the pin 12a, the lever 12 is alsorotated clockwise about the shaft 11, with one end 12b thereof beingmoved to the left, as viewed, to permit the insulator plate 13 to bemoved to the left by the resiliency of the contact 14, so that thecontact 14 is brought into engagement with the contact 16. If theshutter speed dial is then set to a low speed, say, l/ sec. or lower,the forward blade drum 21 and the synchro travel cam 23 are rotated inthe direction of arrow A3 with movement of the forward blade of thefocal plane shutter travelling subsequently to movement of the mirror10a; and when the forward diaphragm assumes its fully open position,that is, the shutter is fully opened, the projection 23:: will actuatethe insulator plate 14b attached to the contact 14a to the right so asto bring the contact 14a into engagement with the contact 19, wherebythe synchro circuit comprising synchro terminal 30b, conductor 20,contact 19, contact 14a, contact 16, conductor 29 and terminal 30a, willbe completely closed to close X contact.

If the shutter speed dial is set to a high speed, the portion 28b of thecam 28 is brought into engagement with the portion 26a of the lever 26so that the insulating pin 25, provided at one end of this lever,actuates the one end 15 of the contact 14a to the right, thuspreestablishing an engagement between the contacts 19 and 14a.Therefore, due to the engagement between the contacts 14 and 16resulting from the shifting of the mirror 10a, the synchro circuit isclosed, thereby to close a high speed contact.

Even in this state, therefore, light will be emitted if an illuminatorsuch as a flash lamp is connected with the synchro terminals 30a and30b.

However, in view of the fact that such synchro-tuning circuit for theillumination as described above is not used when a picture is taken bythe use of the abovedescribed automatic aperture control device, thepresent invention proposes to lead conductors 31c and 31d out of theaperture control device and connect these conductors with the synchroterminals 30a and 30b by means of terminals 31a, 31b, respectively.

The result is that if a shutter button is depressed after a properexposure has been determined by the automatic aperture control device,the mirror will be pivotally moved up to intercept the light passed tothe photoelectric element, which will thus be darkened so that theaperture control motor M will start to revolve and attempt to open theaperture. Nevertheless, the synchro contacts are closed to short-circuitthe base and emitter of the transistor T4 to equalize the potentialsthereat, so that the transistor T4 is immediately turned off to blockthe attempt of the drive system to open the aperture, thus preventingthe aperture from being opened any further. Thus, just prior todepression of shutter button, there is provided a proper exposure set bythe automatic aperture control mechanism.

Strictly speaking, in the construction shown, the closing of the Xcontact takes place somewhat later than the closing of the high-speedcontact and this may result in a slightly greater error than when thehigh-speed contact is used. As is well known, however, in the focalplane shutter, the use of the X contact is limited to relatively mediumand low shutter speeds and the drive system, which attempts to open theaperture, is completely disconnected when the forward blade has beenopened. Therefore, a practically sufficient accuracy of aperture controlmay be achieved with the photoresponsive characteristic of the entiredrive system taken into account. From this, it will be clear that if thesynchro mechanism in use is of the type such as a twosocket type ormanual change-over type, the highspeed contacts may be connected withthe terminals 31a and 31b. Also, if the synchro mechanism in use is ofthe type in which the closing time of the synchro contacts are variablein accordance with the type of a flash bulb used, then the terminals 31aand 31b may be connected with the synchro contacts in such a manner thatthey may be closed earliest after the depression of shutter button.

It will thus be appreciated that the present invention is not limited tothe synchro mechanism shown, but it is also applicable to a camera witha lens shutter, in which case the aforesaid terminals 31a and 31b may beconnected with M contacts adapted to close before the lens shutterblades are opened.

Thus, during photography using an automatic aperture control device, thepresent invention can prevent such aperture control device from beingadversely affected by the quick return mirror, the light receivingelement or the optical member for directing the exposure metering lightto the light receiving element when they are retracted from phototakinglight path in response to the shutter release button or the like, andthis eliminates any possibility that the proper exposure for an objectto be photographed may be hampered.

Furthermore, the present invention requires no such complex circuitry asa memory circuit, but requires only a very simple construction toachieve the purpose described above.

I believe that the construction and operation of my novel camera withautomatic aperture control device will be fully understood and that itsadvantages will be appreciated by those persons skilled in the art.

I claim:

1. An automatic aperture control device for a singlelens reflex camera,comprising:

photoelectric conversion means (T1, T2, R1, R2, Rv,

Rc) for converting into an electrical signal the intensity of lightpassed from an object through an objective lens, said photoelectricconversion means including a photoelectric element disposed so that thelight passed thereto through said objective lens may be reduced afteractuation of a shutter control,

driving means (M, 33, 34, 35) for adjusting the size of diaphragmaperture of said objective lens, said driving means being connected tosaid aperture control means and including one motor,

controlling means (T3, T4, R3, R4, T5, T6, 31d, 310) for controllingsaid driving means, said controlling means including a first controllingmeans (T3, T4, R3, R4, T5, T6) for controlling said driving means inresponse to said electric signal from said photoelectric conversionmeans and second controlling means (31d, 31c) for stopping said drivingmeans, and

synchro contact means for flash photography adapted to be closed at thelatest when the shutter of the camera is fully opened, said synchrocontact means being connected to said stopping means to stop saiddriving means after the synchro contact means is closed.

2. An automatic aperture control device according to claim 1, whereinsaid photoelectric conversion means generates a first electric signal ina case of under exposure and a second electric signal in a case ofoverexposure; said second controlling means includes first means (T4,T6) adapted to be actuated by said first signal so that the size of thediaphragm aperture may be enlarged, and second means (T3, T5) adapted tobe actuated by said second signal so that the size of the diaphragmaperture may be reduced, said first means being connected to saidsynchro contact means through said second controlling means so that theclosure of said synchro contact means renders said first meansnon-operative.

3. An automatic aperture control device according to claim 2, whereinsaid first means include a transistor the base and emitter terminals ofwhich are connected to said second controlling means, said transistorbeing conductive when said controlling means is actuated, andnonconductive when said synchro contact means is closed wherefor saiddriving means is stopped.

I UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.772,974 Dated November 20, 1973 Invent JUN SHIMOMURA It is certifiedthat error appears in the aboveidentified patent and that said LettersPatent are hereby corrected as shown below:

Column 5, line 7, change "RC" to Rc Column 8, line 5, delete "said";

line 25, change "second" to first i $gned.and sealed this 2nd day ofJu1y'l97L (SEAL) Attest:

EDWARD M. FLETCHER,JR. C.MARSHALL DANN Attesting Officer Commissioner ofPatents FORM PO-105O (10-69) v v UCOMWDC 60373.", US, GOVIINHINI PIIMING OHICI: H! O- JPJJ I UNITED STATES PATENII OFFICE CERTIFICATE OFCORRECTION Patent No. 3,772,974 Dated Nov r 20, 1973 Inventor( It iscertified that error appears in the above-identified patent 'and thatsaid Letters Patent are hereby corrected as shown below:

Column 5, line 7, change "RC" to Rc Column 8, line i 5, delete "said";

line'25, change '"second" to first Signed and sealed this 2nd; day ofJuly 1974 (SEAL) Attest: C

EDWARD M. FLETCHER,JR. C.MARSHALL DANN Attesting Officer Commissioner ofPatents FORM po'wso 7 I USCOMM-DC waits-1:09 UIS. GOVIINIINT PRINTINGOFFICI: l9! 0-35-8

1. An automatic aperture control device for a single-lens reflex camera,comprising: photoelectric conversion means (T1, T2, R1, R2, Rv, Rc) forconverting into an electrical signal the intensity of light passed froman object through an objective lens, said photoelectric conversion meansincluding a photoelectric element disposed so that the light passedthereto through said objective lens may be reduced after actuation of ashutter control, driving means (M, 33, 34, 35) for adjusting the size ofdiaphragm aperture of said objective lens, said driving means beingconnected to said aperture control means and including one motor,controlling means (T3, T4, R3, R4, T5, T6, 31d, 31c) for controllingsaid driving means, said controlling means including a first controllingmeans (T3, T4, R3, R4, T5, T6) for controlling said driving means inresponse to said electric signal from said photoelectric conversionmeans and second controlling means (31d, 31c) for stopping said drivingmeans, and synchro contact means for flash photography adapted to beclosed at the latest when the shutter of the camera is fully opened,said synchro contact means being connected to said stopping means tostop said driving means after the synchro contact means is closed.
 2. Anautomatic aperture control device according to claim 1, wherein saidphotoelectric conversion means generates a first electric signal in acase of under-exposure and a second electric signal in a case ofover-exposure; said second controlling means includes first means (T4,T6) adapted to be actuated by said first signal so that the size of thediaphragm aperture may be enlarged, and second means (T3, T5) adapted tobe actuated by said second signal so that the size of the diaphragmaperture may be reduced, said first means being connected to saidsynchro contact means through said second controlling means so that theclosure of said synchro contact means renders said first meansnon-operative.
 3. An automatic aperture control device according toclaim 2, wherein said first means include a transistor the base andemitter terminals of which are connected to said second controllingmeans, said transistor being conductive when said controlling means isactuated, and nonconductive when said synchro contact means is closedwherefor said driving means is stopped.